My truck is a 2003 6.0 F350. I was recently under the hood installing new batteries, and I decided to check the EGR valve. The connector fell off my valve about 20,000 miles ago, so it has been in the closed position all this time. The smog test here in Ontario only checks for particulate matter in the exhaust, not NOx, so it passed the test with the connector off.

When I removed the valve, I was surprised to see that it was very clean, with no carbon build-up, only a little oily black residue. I looked down inside the manifold at the passages, and they were also quite clean. Running with the valve closed doesn't allow any exhaust flow through the EGR cooler, because there is nowhere for the gas to exit, and this must be the reason for the clean valve.

Like many others, I used to have EGR valve problems before the connector fell off, and had cleaned it several times. Very hard black carbon used to build up on the valve.

In my truck, there is no CEL or codes generated by the disconnection. Performance and fuel economy seems not to be affected, except for possible faster spool-up of the turbo under light load conditions. The truck is primarily used for hauling a 11,000 lb fifthwheel RV.

I thought I would report these results, because I know thjere have been many, many threads on the subject of the EGR valve and disconnection.

I'm hoping that with the absence of exhaust flow through the EGR cooler (there is nowhere for the gas to exit) the cooler will be less subject to heat-related issues. Even though the cooler is still open to the exhaust at the back end, no flow can occur, so heat input from the exhaust would be minimal.

I would be interested to hear other people's experiences with this.